Are There Differences Between Intradermal and Intramuscular Injections of Botulinum Toxin on the Forehead?

Abstract

The intradermal technique to inject botulinum toxin is a popular procedure in upper facial rejuvenation to minimize side effects, such as brow ptosis, and can sometimes result in a lifting effect. The present study investigated differences in effects according to injection modality. Fifteen women received intradermal injections of botulinum toxin (total dose, 8U) into the forehead, and 14 women received intramuscular injections. The maximal antiwrinkle effect was recorded at Week 2, and the duration of the effect was the same in both groups. The brow position was lowered at Weeks 2 and 4 in the intramuscular injection group and was preserved in the intradermal injection group throughout the follow-up period. The amount of maximal voluntary eyebrow movement was decreased at Weeks 2 and 4 and recovered at Week 16 in both groups. The change in the electromyographic amplitude of the frontalis muscle was prolonged until Week 16 in both groups. Subjective satisfaction with wrinkles was similar in both groups. However, the intradermal injection was more painful. Intradermal injection of botulinum toxin is a safe and effective method to improve forehead rhytides.